Detection of an Antigen (AN6520), Possibly Related to Non-A, Non-B Hepatitis, by Monoclonal Antibodies. I

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Abstract
The antibody to AN6520 antigen, which was isolated from the liver of a patient with non‐A, non‐B hepatitis (NANBH), has been detected frequently in convalescent sera from patients with NANBH by the passive hemagglutination (PHA) test. In a further study, we established hybridoma cells secreting antibodies against AN6520 antigen and obtained ascitic fluids with PHA titers ranging from 1: 105 to 1: 107. In immunodiffusion with AN6520 antigen, all monoclonal antibodies were found to form an identical precipitin line. These lines were also identical to those formed by rabbit antiserum against AN6520 antigen and by convalescent sera from patients with NANBH. With one of the monoclonal antibodies, 1‐F12, solidphase radioimmunoassay (SP‐RIA) for detecting AN6520 antigen was developed as well as blocking RIA for anti‐AN6520 antibody detection. The antigen assay was 50 times more sensitive than the reverse passive hemagglutination (R‐PHA) test, with a sensitivity threshold of the 1 ng/ml of antigen solution; the antibody assay was 10 times more sensitive than PHA. The results with this blocking RIA were mostly in agreement with the data obtained by PHA. Furthermore, the antigen in human sera, which had never been detected by R‐PHA test, could be detected by SP‐RIA.